Weft monitoring system for a weaving machine and a method of monitoring weft thread

ABSTRACT

The monitoring period consists of a first portion in which the total number of yarn loops which deviate from the picking path and fall outside the monitoring beam are counted and a second portion in which the total time for which the loops formed during this portion remain outside the picking path is calculated. A first voltage signal is produced corresponding to the total number of loops in the first portion and a second voltage signal is produced corresponding to the total number of loops and the total time duration of such for the two portions. These signals are integrated to give a resultant voltage signal which is compared to a reference voltage signal for the yarn being picked. If the reference voltage signal is exceeded, the weaving machine is stopped and/or an alarm is given. If not, the machine continues to operate.

United States Patent 1191 Meyer et al.

Apr. 9, 197 4 WEFT MONITORING SYSTEM FOR A WEAVING MACHINE AND A METHOD OF MONITORING WEFT THREAD Inventors: Alfred Meyer, Winterthur; Thomas Banziger, Goldach, both of Switzerland Sulzer Brothers, Ltd., Winterthur, Switzerland Filed: Jan. 9, 1973 Appl. No.:- 322,208

Foreign Application Priority Data Assignee:

US. Cl. 139/370 Int. Cl. D03d 51/18, D03d 51/34 Field of Search 139/273, 336, 353, 370,

References Cited UNITED STATES PATENTS 10/1970 Schlappi 139/370 9/1971 Hohener 139/370 7/1972 Gotoh 139/370 Primary Examiner-l-lenry S. Jaudon Attorney, Agent, or Firml(enyon & Kenyon Reilly Carr & Chapin 15 7] ABSTRACT The monitoring period consists of a first portion in which the total number of yarn loops which deviate from the picking path and fall outside the monitoring beam are counted and a second portion in which the total time for which the loops formed during this portion remain outside the picking path is calculated. A

first voltage signal is produced corresponding to the total number of loops in the first portion and a second voltage signal is produced corresponding to the total number of loops and the total time duration of such for the two portions. These signals are integrated to give a resultant voltage signal which is compared to a reference voltage signal for the yarn being picked. If the reference voltage signal is exceeded, the weaving machine is stopped and/or an alarm is given. If not, the machine continues to operate.

4 Claims, 3 Drawing Figures SHEET 1 BF 2 MENTEB APR 9 I974 WEFT MONITORING SYSTEM FOR A WEAVING MACHINE AND A METHOD OF MONITORING WEFT THREAD This invention relates to a weft monitoring system for a weaving machine and to a method of monitoring weft thread. I

Various systems and techniques have been known for monitoring weft picking in weaving machines. For example, use has been made of a weft stop motion in which a transmitter transmits a beam in the weft direction and .a receiver receives the beam, I the receiver being associated with circuitry which stops the machine and/0r operates a warning system in the event of an incompletely picked or untensioned or broken weft yarn. However, the known weft stop motions may occasionally cause false stops of the machine. The explanation for this is that a weft yarn oscillates transversely of the weft-shooting direction during the time that yarn is being monitored, and if the departure of the weft yarn from the shooting line, i.e. from, the ideal path, is such that the yarn moves outside the detecting beam, the beam receiver thinks that no weft yarn has been picked, and so the weaving machine is stopped.

Further, a weft yarn which breaks during picking behaves rather like a picked weft yarn which is oscillating transversely due to beingfupset on the catching side upon cessation of braking and pull-back of the weft. A broken weft yarn might therefore fail to be detected since the weft stop motion might see the broken yarn as an unbrokenyarn producing loops, in which event the machine would not be stopped.

Accordingly, it is an object of the invention to ensure that a weft stop motion stops a weaving machine only in the absence of a pick.

No pick as used in this description means a weft yarn lost during picking, a weft yarn which has been picked but subsequently pulled out of the shuttle when the shuttle is already in a catcher, and a weft yarn which has been picked but which is lying loosely in a wide loop in the shed.

It is another object of the invention to be able to make a distinction between a picked loop-producing weft yarn and a broken weft yarn during monitoring of a pick.

I The underlying bases of the method according to the invention are as follows:

During a monitoring period, the amounts by which the loops of an unbroken weft yarn depart from the shooting line decrease since the pull-back of the yarn tends to stretch the weft yarn; whereas the departure or deviation of the loops of a broken weft yam from the weft line tends to decrease more slowly, particularly during the second half of the monitoring period. The loop-forming frequency of an unbroken weft yarn during the monitoring period depends upon the weft braking pattern. When a weft yarn breaks, the braking effect on the yarn decreases, and since the broken weft yarn piles up at the catcher, the number of loops produced during the monitoring period increases. It has been found byexperience that with thin weft yarns, the deviations or departures of the loops from the shooting line are very high whereas with thick weft yarns the number of loops are very high. However, a single weft stop motion is required to be able to monitor a very wide range of weft yarn diameters. Also, it has been found that both the number of loops and the departures from the shooting line are below the extreme values for broken wefts of average diameters, and so both these considerations are allowed for;

To this end, according to the invention, throughout the monitoring period alloted to one pick, a first signal is formed for each loop formed by the weft yarn which deviates so far away from the weft-shooting line that the weft yarn leaves the monitoring beam. These first signals are added to form a first summation signal proportional to the number of loops. Further, substantially during the second half of the monitoring period, a second signal is also formed for each loop of weft yarn which deviates so far away from the weft-shooting line or picking path that the weft yarn leaves the monitoring beam. The magnitude of the second signal corresponds to the time for which the particular weft yarn loop concerned remains outside the beam. The first and second signals for each loop are added to form third signals which are, in turn, added to form a second summation signal corresponding to the total out-of-beam dwell time of the particular weft yarn concerned. The first and second summation signals are then added to form a third summation signal which is compared with a reference value. If this reference value is exceeded, the circuitry of the monitoring system stops the machine and/or operates a warning device.

In the method according to the invention, the weft yarn has a chance of forming a number of loops which depart far enough from the shooting line to be outside the sensing beam before the weft stop motion puts a no pick interpretation on matters and stops the machine. Also, the yarn must remain outside the beam for a relatively long time before the weft stop motion interprets this absence as noweft yarn present and stops the machine. The method according to the invention can also be used to detect whether a picked weft has broken, so that the machine can also be stopped in this case..

The monitoring system of the invention includes an electrical or electronic circuit comprising a weft sensing device, an amplifier, a comparator, a store, a pulse shaper, an And-gate, two make devices, an adder, an

integrator, a second comparator, a reference voltage source and a switch or alarm device.

The weft sensing device is of any suitable type such as a photoelectric type for producing a voltage in response to the absence of a weft yarn from a predetermined yarn or pick path. This deviceis connected to an input of the amplifier while the output of the amplifier is connected to the comparator. The amplifier functions in a known manner to transmita received signal to the comparator.

The store is also connected to a second input of the comparator to deliver a signal voltage of a value corresponding to the absence of a weft yarn in the pick path. The signal voltage also corresponds to the voltage that should be present at the amplifier output in the absence of a weft yarn from the pick path.

The output of the comparator connects to an inpu of the And-gate and to an input of the pulse shaper. in addition, one make device has an output connected to a second input of the And-gate while the other make device has an output connected to a second input of the pulse shaper. These make devices function to deliver a voltage to the respective And-gate and pulse shaper for each pick at predetermined times. The first time occurs during a first portion of the monitoring period and the second time during a later portion of the monitoring period. During the first portion of period, the make device connected to the puse shaper transmits a voltage thereto. If the comparator also transmits a voltage, indicative of a loop deviating from the pick ing path, a signal or pulse is produced. This occurs for each loop that falls outside the picking path. During the second portion of the period, the other make device connected to the And-gate transmits a voltage. If the comparator also transmits a voltage, indicative of the duration of time the loop of yarns stay out of the picking path, a signal or pulse is produced at the output of the And-gate corresponding to the time out-of-thepicking path. This occurs for each loop that falls outside the picking path in the second portion of the period.

The adder has an input connected to the outputs of the pulse shaper and And-gate to receive the pulses therefrom. The adder first transmits the pulses from the pulse shaper during the first portion of a monitoring period to the integrator which adds the pulse to form and stores a first summation signal proportional to the number of yarn loops. During the second portion of the monitoring period, the adder adds the pulse received from the pulse shaper and And-gate and supplies the result to the integrator which, in turn, determines the total summation signal corresponding to the total time the weft yarn remains outside the picking path. The integrator also integrates the voltages of the two summation signals to form a third summation signal of a voltage corresponding to the number of weft loops formed and to the total time of the loops out of the picking path up to that point in time.

The output of the integrator connects to an input of the second comparator to deliver the third summation signal thereto for comparison with a reference voltage from the reference voltage source. This reference voltage can be determined by experience for various yarn types and sizes and can be adjusted to suit the yarn being monitored. If the voltage of the third summation signal exceeds the reference voltage, the comparator signals the switching device to set off an alarm and/or to stop the weaving machine. If the reference voltage is not exceeded, then the weaving machine continues operation.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a view from the cloth end of a weaving machine incorporating a weft monitoring system according to the invention;

FIG. 2 schematically illustrates a block diagram of a electrical circuit for a weft monitoring system according to the invention; and

FIG. 3 illustrates a time/voltage diagram for a weft monitoring system according to the invention.

Referring to FIG. 1, the weaving machinehas two uprights 1, 2 between which are mounted, in known fashion, a warp beam (not shown),'a cloth beam 3, guiding and tensioning means (not shown) for the warp and for the cloth, a central bearer 4 interconnecting the two uprights l, 2 and a main drive shaft 5. Also a shaft 6 forming part of a shedding mechanism and a reed 7 are mounted between the uprights 1, 2.

A shuttle-shooting mechanism 8 is disposed on upright 1 and a catcher 9 is disposed on the right-hand side of the machine. The catcher 9 is adapted to catch the shuttle at the end of a shooting or picking step. Weft yarn 10 is supplied from a supply bobbin 1], which is, as a rule, non-displaceably disposed outside the shed, via a screen 12 and via a vertically moving yarn tensioner 13. The weft yarn 10 is picked into the shed in any known manner. After each pick, the shuttle in the catcher 9 is moved back a little so as to always be in exactly the same position after each pick or shot. During this time, the yarn tensioner 13 moves into its top position so that the weft yarn remains stretched while the shuttle moves back. Yarn brakes (not shown) are operative during the pushing-back of the shuttle to make sure that the resulting deviation at the tensioner 13' is formed mainly by a pulling-back of the picked weft yarn; if necessary, some extra yarn can be pulled off the bobbin 11.

After the backwards movement of the shuttle and weft yarn, the weft yarn is severed by shears (not shown) on the shooting side. After beating-up and shed-changing, the projecting weft yarn ends on both sides of the shed are introduced into the next shed by a selvedging mechanism (not shown). The finished cloth is wound on the cloth beam 3.

A casing is secured to the catcher 9 below the picking or shooting line, i.e. the theoretical shuttle track or path, and houses a sensing-beam transmitter, in the form of a luminescent diode 21 (FIG. 2). A second casing 22 in which a radiation-sensitive element in the form of a photodetector 23 (FIG. 2) is disposed is also secured to the catcher 9.

Referring to FIG. 2, the diode 21 emits a beam 24 which is bunched by an optical system 26 and which is aimed at the photodetector 23 transversely of the picking or shooting line 27 (which extends transversely of the plane of the drawing in FIG. 2), of a weft yarn 28. A box which contains the electrical circuitry of the weft stop motion is mounted on the right-hand upright 2 as viewed in FIG. 1. As shown in FIG. 2, the circuitry includes an amplifier whose input 30a is connected to the photodetector 23 and whose output 30b is connected to an input 31a of a comparator 31. The comparator 31 has a second input 31b which is supplied with a constant voltage. This latter voltage is equal to the signal voltage which, in the absence of a weft yarn 28 in the beam 24, is present at the amplifier output 30b and therefore at comparator input 31a. This voltage is shown in FIG. 3 as an unblanking voltage U and is stored in a store 47. The storage of the voltage U provides a means of compensating for dirt in the optical system 26.

An output 316 of comparator 31 is connected to one input 32a of an And-gate 32 and to one input 33a of a pulse shaper or monostable multivibrator 33. A second input 32b of the And-gate 32 is connected to a switching device 34 which at every pick applies a voltage to the And-gate input 32b at a particular time in synchronization with the arriving shuttles of the machine. A second input 33b of the multivibrator 33 is connected to a switching device 35 which is also in synchronization with the arriving shuttles in order to apply a voltage at each pick to the multivibrator input 33b at a particular time.

An output 320 of the And-gate 32 is connected to an input 36a of an adder 36. An output 330 of the multivibrator 33 is connected to a second input 36b of adder 36. An output 36c of the adder 36 is connected to an input 37a of an integrator 37 whose output 37b is connected to an input 38a of a second comparator 38. A second input 38b of this comparator 38 is connected to a source 39 of an adjustable reference voltage U and an output 380 of the comparator 38 is connected to a switching device 40 which switches off the machine and/or operates a warning system in the absence of pick or in the event of a weft yarn break.

Referring to FIG. 3, the timer is plotted along the abscissa and voltage is plotted along the ordinate. Portion A of FIG. 3, shows the pattern of the signal voltage which appears at the amplifier output 30b in the case of a picked healthy weft yarn. While the shuttle is actually moving through the beam 24, the voltage U decreases to the value U and returns to the yarn signal voltage after the shuttle has passed through the beam 24. The voltage variations which occur at the amplifier output 30b because of looping of the yarn 28 are recorded until the time 1 i.e. the time at which the shuttle has been pushed back from the catcher 9 and, in so doing, masks the beam 24 again. The weft monitoring period extends from the time t, to the time t;,. Clearly, the number of loops which the weftyarn forms during the first portion t,t of the total monitoring period t,-t is much greater than during the second portion t -t During the portion t,t the fact that a broken weft yarn tends to make more loops than an unbroken one is allowed for by the number of loops being counted. The term loops as used now and hereinafter always denotes loops whose deviation from the picking line is 7 large enough for the weft yarn to depart from the sensing beam. As long as the'number of loops stays below a critical value, the weft stop motion interprets this I state of affairs as indicating that the weft yarn is unbroken, and so the machine is not stopped. This is the first criterion for monitoring. If the weft yarn departs from the detecting beam 24 more frequently than corresponds to the preset number of loops, the first criterion ceases to be met and the weft stop motion stops the machine.

The greater deviation or departure of the loops during the period z -t is allowed for by calculating the time for which a weft yarn is outside the beam. If the latter time is below a critical value, the weft stop motion interprets this state of affairs as meansing that the weft yarn is unbroken and so the machine is not stopped. This is the second monitoring criterion. If no weft yarn has been picked, the second criterion fails to be met .and the machine is stopped. How monitoring proceeds in the light of these two criteria will be described with reference to the operation of the system.

Portion B of FIG. 3 represents the pattern of signal voltage which appears at amplifier output 30b in the case of a broken weft yarn. The references are the same in portion B as in portion A except that they have an apostrophe. Clearly, the number of yarn loops during the first period t, of the monitoring period t, t';, is much greater than during the period t t' a broken weft yarn remains outside the beam. In order to take account of this different behavior of a broken weft yarn during the monitoring period, the weft yarn monitoring is again based on two criteria similar to the monitoring of an unbroken weft yarn.

Monitoring of the weft yarn on the basis of the various criteria proceeds as follows:

Towards the end of a picking operation, as soon as the moving shuttle clears the sensing beam at the time t,, the multivibrator input 33b receives an applied voltage via the make device 35. This is followed by a delay. It will first be assumed that an unbroken weft yarn has been picked. The voltage at amplifier output 30b at the time t, is the voltage U If the weft yarn forms loops with departures which do not cause the weft yarn to move out of the beam 24, the output voltage of the amplifier 30 which appears at the comparator input 31a is smaller than the voltage U at the comparator input 31b- For this condition, the comparator 31 is constructed to produce a voltage at output 310. The latter voltage disappears for each return of the weft yarn back into the beam 24. The voltages delivered at the comparator output 310 are supplied to the And-gate input 32a and to the multivibrator input 33a. This has no effect on the And-gate 32 since the input 32b is still without signal, and so the And-gate 32 remains nonconductive.

However, as the multivibrator input 33b had a voltage applied thereto via the switching device 35 as early as the time t,, i.e. at the beginning of the monitoring period t, t the voltage delivered from the comparator 31 causes the multivibrator 33 to produce a brief voltage 33d for each signal produced by the comparator 31 and appearing at the multivibrator input 33a. Thus a brief voltage 33d has a constant length of duration t,,, and lasts throughout the complete monitoring period t The voltages, in the form of signals or pulses, 33d are supplied via the adder 36 to the integrator input 37a. The integrator 37 adds the pulses 33d together to form a voltage U proportional to the number of weftyarn loops. The integrator 37 then stores the voltage U At any time of the monitoring period t, t the voltage U corresponds to the number of loops formed by the weft yarn up to the time t and having departures from the picking line in which the weft yarn leaves the beam 24.

Monitoring according to the second criterion starts at the time t of the monitoring period t t Of course, the voltages appearing at the comparator output 310 in response to weft looping are of a duration corresponding to the time for which the weft yarn stays outside the beam 24. These signals are processed as follows: at the time t the And-gate input 32b has a voltage applied by the switching device 34. As a result, the gate 32 gates signals 40 which appear at the input 32a and which the comparator 31 produced during the period .t corresponding to the behavior of the weft yarn in the latter period. The signals 40 are applied via the input 36a to the adder 36 where the signals 40 are additively associated with the signals 33d appearing at adder input 36b. The signals corresponding to the addition of the two signals 33d, 40 appear at the adder output 36c and are supplied via the input 37a to the integrator 37 which determines their time integral and produces an output voltage U corresponding to the total time for which the weft yarn remains outside the beam. Also, the integrator 37 integrates the voltage. U and the voltage U previously stored in integrator 37 to form a voltage U i.e. a voltage corresponding, at any time t of the period t, t;,, to the number of weft loops fo'rmed up to the time t and to the total time for which the weft yarn has been outside the beam 24 up to the time r of the period t t Voltage U is supplied via the input 380 to the comparator 38 and is In the system described, weft yarn behavior is detected by means of a detecting or sensing beam emitted by a luminescent diode; however, a sensing beam of a different wave length can of course be used, as can a sensing beam of some other kind, such as a sonic beam or an air stream. Also, the method can be carried into effect not, as described, using electronic elements but using other, e.g. pneumatic, elements.

What is claimed is: 1. A method of monitoring weft picking in a weaving machine wherein a weft yarn is passed through a picking path comprising the steps of forming a first signal for each loop of yarn deviating from the picking path during a monitoring period;

adding said first signals during a first portion of said monitoring period to form a first summation signal proportional to the total number of loops in said first portion;

forming a second signal for each loop of yarn deviating from the picking path during a second later portion of the monitoring cycle, with the magnitude of said second signal corresponding to the time the respective loop of yam remains outside the picking path;

adding said first signals and said second signal for a respective loop during said second portion to form a third signal;

adding said third signals during said second portion to form a second summation signal proportional to the total out-of-picking path time of the yarn;

adding said first and second summation signals to obtain a third summation signal; and

comparing said third summation signal with a reference value to produce a signal indicative of a nopick in response to said third summation signal exceeding said reference value.

2. A monitoring system for monitoring weft picking in a weaving machine comprising and amplify a signal corresponding to the absence of a weft yarn in the picking path;

a comparator having one input connected to said amplifier to receive an amplified signal therefrom;

a store connected to a second input of said comparator to deliver a preset constant voltage signal thereto;

a monostable multivibrator having one input connected to said comparator to receive a signal therefrom;

a first make device connected to a second input of said multivibrator to deliver a voltage thereto at a first preset time;

an And-gate having one input connected to said comparator to receive a signal therefrom;

a second make device connected to a second input of said And-gate to deliver a voltage thereto at a second preset time later than said first preset time;

an adder-connected to an output of said multivibrator to receive first pulses therefrom corresponding to the occurrence of yarn loops and to an output of said And-gate to receive second pulses therefrom corresponding to the time the yarn loops are out of the picking path while adding said first and second pulses during a later second portion of a monitoring period;

an integrator connected to said adder to receive and add the first pulses from said multivibrator to form a first summation signal during a first portion of the monitoring period and to receive and add the added pulses from said And-gate to form a second summation signal, said integrator forming a third summation signal from said first and second summation signals;

a second comparator having one input connected to said integrator to receive said third summation signal; and

a reference signal source connected to a second input of said second comparator to deliver a reference signal thereto whereby said second comparator emits a signal in response to said third summation signal exceeding said reference signal.

3. A monitoring system as set forth in claim 2 further comprising a switching device connected to said second comparator for receiving said latter signal to stop said weaving machine and/or to activate a warning systern.

4. A monitoring system as set forth in claim 2 wherein said stop motion device is a photoelectric means. 

1. A method of monitoring weft picking in a weaving machine wherein a weft yarn is passed through a picking path comprising the steps of forming a first signal for each loop of yarn deviating from the picking path during a monitoring period; adding said first signals during a first portion of said monitoring period to form a first summation signal proportional to the total number of loops in said first portion; forming a second signal for each loop of yarn deviating from the picking path during a second later portion of the monitoring cycle, with the magnitude of said second signal corresponding to the time the respective loop of yarn remains outside the picking path; adding said first signals and said second signal for a respective loop during said second portion to form a third signal; adding said third signals during said second portion to form a second summation signal proportional to the total out-ofpicking path time of the yarn; adding said first and second summation signals to obtain a third summation signal; and comparing said third summation signal with a reference value to produce a signal indicative of a ''''no-pick'''' in response to said third summation signal exceeding said reference value.
 2. A monitoring system for monitoring weft picking in a weaving machine comprising a weft stop motion for sensing the presence or absence of a weft yarn in a picking path; an amplifier connected to said stop motion to receive and amplify a signal corresponding to the absence of a weft yarn in the picking path; a comparator having one input connected to said amplifier to receive an amplified signal therefrom; a store connected to a second input of said comparator to deliver a preset constant voltage signal thereto; a monostable multivibrator having one input connected to said comparator to receive a signal therefrom; a first make device connected to a second input of said multivibrator to deliver a voltage thereto at a first preset time; an And-gate having one input connected to said comparator to receive a signal therefrom; a second make device connected to a second input of said And-gate to deliver a voltage thereto at a second preset time later than said first preset time; an adder connected to an output of said multivibrator to receive first pulses therefrom corresponding to the occurrence of yarn loops and to an output of said And-gate to receive second pulses therefrom corresponding to the time the yarn loops are out of the picking path while adding said first and second pulses during a later second portion of a monitoring period; an integrator connected to said adder to receive and add the first pulses from said multivibrator to form a first summation signal during a first portion of the monitoring period and to receive and add the added pulses from said And-gate to form a second summation signal, said integrator forming a third summation signal from said first and second summation signals; a second comparator having one input connected to said integrator to receive said third summation signal; and a reference signal source connected to a second input of said second comparator to deliver a reference signal thereto whereby said second comparator emits a signal in response to said third summation signal exceeding said reference signal.
 3. A monitoring system as set forth in claim 2 further comprising a switching device connected to said second comparator for receiving said latter signal to stop said weaving machine and/or to activate a warning system.
 4. A monitoring system as set forth in claim 2 wherein said stop motion device is a photoelectric means. 